Refactor the devserver to make it easier to control caching

chrome/common/extensions/docs/server2/known_issues_data_source.py

-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import csv
-import logging
-import operator
-from StringIO import StringIO
-
-import object_store
-from url_constants import OPEN_ISSUES_CSV_URL, CLOSED_ISSUES_CSV_URL
-
-class KnownIssuesDataSource:
-  """A data source that fetches Apps issues from code.google.com, and returns a
-  list of open and closed issues.
-  """
-  def __init__(self, object_store, url_fetch):
-    self._object_store = object_store
-    self._url_fetch = url_fetch
-
-  def GetIssues(self, url):
-    cached_data = self._object_store.Get(url, object_store.KNOWN_ISSUES).Get()
-    if cached_data is not None:
-      return cached_data
-
-    issues = []
-    response = self._url_fetch.Fetch(url)
-    if response.status_code != 200:
-      logging.warning('Fetching %s gave status code %s.' %
-          (KNOWN_ISSUES_CSV_URL, response.status_code))
-      # Return None so we can do {{^known_issues.open}} in the template.
-      return None
-    issues_reader = csv.DictReader(StringIO(response.content))
-
-    for issue_dict in issues_reader:
-      id = issue_dict.get('ID', '')
-      title = issue_dict.get('Summary', '')
-      if not id or not title:
-        continue
-      issues.append({ 'id': id, 'title': title })
-    issues = sorted(issues, key=operator.itemgetter('title'))
-    self._object_store.Set(url, issues, object_store.KNOWN_ISSUES)
-    return issues
-
-  def get(self, key):
-    return {
-      'open': self.GetIssues(OPEN_ISSUES_CSV_URL),
-      'closed': self.GetIssues(CLOSED_ISSUES_CSV_URL)
-    }.get(key, None)